An electro-optic device, such as an electro-optic IQ phase modulator, may be used to encode data, represented by a set of electrical signals, into the phase and/or amplitude of light as the light passes through the IQ phase modulator. In some IQ phase modulators (e.g., a Mach-Zehnder (MZ) modulator), light (e.g., generated by a light source, such as a laser) is split between an I branch and a Q branch of the modulator, where each branch comprises a series of optical waveguides with a set of electrodes placed along (e.g., on, over, adjacent to, and/or the like) the series of waveguides. In order to enable IQ modulation, the portion of the light in the Q branch is put at 90 degrees (°) out of phase (i.e., at quadrature) from the portion of the light passing through the I branch. For example, respective parent direct current (DC) biases may be applied to electrodes arranged on the I branch and/or the Q branch in order to introduce phase shifts that put the portion of the light in the Q branch at quadrature with the portion of the light in the I branch. Other types of branches may be possible that are different from an I branch and a Q branch for a combined interferometer structure, such as for a modulator.
In the IQ modulator, the portions of the light are further split between arms of each branch (e.g., left and right arms of the I branch, and left and right arms of the Q branch). Although arms may be referred to in terms of left and right, other orientations may be possible. In order to encode data in each portion of the light while passing through the IQ phase modulator, a first electrical signal (e.g., a radio frequency (RF) signal) is differentially applied to electrodes on the left and right I arms (herein referred to as an I signal), while a second electrical signal is differentially applied to electrodes on the left and right Q arms (herein referred to as a Q signal). The I signal and the Q signal represent the data to be encoded in the phase and/or the amplitude of the light. Applying the I signal and the Q signal to the respective arms provides amplitude modulation and/or phase modulation of the light passing through the I and Q branches, respectively (e.g., for QPSK phase modulation may be performed, for QAM amplitude modulation and phase modulation may be performed, etc.). The modulated portions of the light are then recombined in the modulator to form modulated output light. Here, the amplitude and/or the phase of modulated output light are a result of the application of the I signal and the Q signal and, thus, the modulated output light carries the data.